Drive mechanism



Jan. 30, 1951 E. B. OFFUTT I 2,539,858

DRIVE MECHANISM Filed May 12, 1947 2 Sheets-Sheet l NAG/V5 TIC 8500/? DER mEmZQr ELMER- B. OFFUTT.

E. B. OFFUTT DRIVE MECHANISM Jan. 30, 1951 2 Sheets-Sheet 2 Filed May 12, 1947 Patented Jan. 30, 1951 UNITED STATES PATENT OFFICE i DRIVE MECHANISM Elmer B. Oifutt, Kansas City, Mo., assignor to The Indiana Steel Products Company, Chicago, IlL, a corporation of Indiana Application May 12, 1947, Serial No. 747,556

3 Claims.

mechanism maintains the drive in good operating condition.

Further, it is an object of my invention to provide an improved drive system for imparting linear velocity to a belt-like medium such as paper tape which is particularly adapted for use.

in connection with magnetic recording and reproducing equipment.

Yet another object of my invention is to provide an improved drive member for imparting controlled velocities to a medium such as paper or the like.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself,however, both as to its organization and.

method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings,

On the drawings:

Figure 1 is a somewhat diagrammatic top view of a magnetic recording and reproducing mechanism incorporating the features of my invention.

Figure 2 is a somewhat diagrammatic view of the mechanism of Figure 1 as seen with the top removed.

Figure 3 is a side view of the apparatus of Figures 1 and 2 but with the medium removed, and Figure 4 is a cross section view through th drive member of Figure 1.

As shown on the drawings:

In Figure 1, Id and I2 are supporting devices for the lengthy medium I4, in the particular structure shown, II! and I2 are spools and medium I4 is a paper tape such as manila rope stock treated for use in a magnetic recorder. This treatment may, for example, comprise a coating of. magnetic particles obtained bypassing the paper through a vinyl acetate-acetone solution containing suspended magnetic particles. In passing between spools Ill and I2, medium l4 passes over drive capstan I6 and recording and reproducing head I8. Head I8 is electrically connected to unit 20 which is a magnetic recorder and reproducer. Recorder and reproducer 20 is arranged so that in the recording operation time variations in the intensity of a signal, such as speech or music, are converted into corresponding time variations in the magnetic field about head I8. Thus, as the medium I4 is passed under head I8 at controlled linear velocity, the degree of magnetization thereof along its length is altered in accordance with the time variations in the signal applied to recorder 20, thereby imparting to medium I4 longitudinal variations in magnetization in accordance with the impressed signal. In the reproducing operation, magnetic recorder and reproducer 20 is connected so that the induced voltages in head I8 associated with time variations in' the magnetic field caused by the variations in magnetization of medium I4 as it passes thereover are converted into corresponding signal variations, such as, for example, the

. intensity of a sound wave, thereby reproducing the signal corresponding to the magnetization of medium I4.

It is the purpose of motor 22, Figures 2 and 3, to rotate capstan IE so as to impart linear velocity to medium I4. Flywheel 24 maintains substantially constant the rotational velocity of capstan I6 despite random variations in the torques applied to the shaft of motor 22, thereby causing the peripheral velocity of capstan I6 to be maintained substantially constant. In addition to driving capstan I6, motor 22 is connected by pulley 26 to' tend to drive spools III and I2 in respective opposite directions so as-to tend to cause medium I4 to wind on both spools acting in opposition to each other. This tendency is imparted to spool III by belt 28 which rides on pulley 26 and pulley 30. 'A controllable tension is placed on belt 28 by idler pulley 32, the magnitude of this tension being determined by the position of mounting plate 34 about axis 36. Spool I2 tends to be driven in the windup direction by means of belt 38 which rides on pulley 40.

The diameters of pulleys 26, 30 and 40 are so proportioned relative to the diameter of capstan I6 that medium I4 tends to wind upon spool I2 at a rate greater than it tends to pass across capstan I6. As a consequence, medium I4 is maintained taut between capstan I6 and spool I2.

It is-the function of pinch wheel 42 to urge medium" liagainst capstan I6 so as to achieve pressure therebetween and a good frictional engagement. As will be evident from Figure 2, this wheel is mounted upon spindle 44 which is supported by plate 34 so that as plate 34 is twisted in the clockwise direction relative to axis 36, the frictional engagement between medium I4 and capstan I 6 is increased. From Figure 2 it will further be evidentthat'clockwiserotation of plate 34 aboutaxis 36 swingsidler pulley'32 in a disengaging direction so as to cause pulley 28 to .1 assume a loose condition. The position of plate- 34 about axis 36 is determined by operating-,han-- dle 46 which projects above the unit as shown in Figures 1 and 3.

When operating handle 461'is ir'r-the"forward' position shown in the solid lines of Figure 1, the belt 28 is in a relatively loose condition and; slips over pulleys 26 and 30 with relative ease. Furthermore, the pressure exerted between pinch wheel 42 and capstan I 6 is relatively great and causes; goodafric tional :engagement rbetweentmedi'um .I 4'iand the surface offcapstan" I 6; thusilime parting; linear velocity to: medium; I 4': of value? corresponding to stherangular velocity of :capstan" I 65. Thus.:the:--a'ctionof capstanilfia overcomes the action ofbelt 1 28 i and" .medium I4: is with;- drawn from spool IE]: ata? controllable? linear: velocity; determined by: the: angular:- velocity?" of capstan I6: Simultaneously, medium :I t 'is Wound upon-spool I2by-reasoniof*the'iactioniof:belt 38? 30 Since belt-38 tends to drive spjool l 2 at an angular velocity; exceeding, that. corresponding: to the linear velocity imparted by capstan IStomedium I4, belt 38 'slipsand'medium: I4 -is:held:taut bee tween. capstan I 6 Etl'ld'SIlOOlt' I 2..

When: operating handle/46: is rotatedirrzthea counterclockwisedirection to the position shown" inizthe :dashedlinesof Figure F1; pinchpulley '42-; isiswung; to a disengaging position'melative' to capstan I 6-asxshown by:the dashed lines of Fi 40 ure 1.: In. this :'condition;zwheel' 42 does'not press medium- I4-against :capstan I G but instead per mits that :pressure: to assumethe' relatively small value associated with the-torque of belts'ZS and: 38 =tending-to-rotate spools I8 and; I2; Simul- 45 taneouslyywheel 32 swings againstbeltlzt in? direction to increase the tension thereof, thereby increasing the frictional engagement between that-belt.and fpulleys 26 a-nd- 30.. In thiscondi tion, the.torqueexertedi'on spool Iii as a conse-- 5 quence of pulley-38 is:sufiiciently; great to' over-- cOme-the reduced winding forces associated with rotationof capstan: I6"and-. thetendency of belt 3azto-rotate-spool1 I2-=in-' the direction to windmedium I4 thereon; Medium lllaisaccordinglytransferred from spool I2 -to*spool IE3. atlinear-- velocity corresponding to. the angular: velocity? ofrspoolli! and the-body ofrthe medium1I4 con tainedron that spool;-

From theabove idescriptioninf-operation; it will be evident that 'operatiorrlof thesmechanism'of Figures 1,2 and '3 depends.=entirely--on;the-fric tionalengagement between medium? I l' andcapstan: Iii-tofim-partz uniform: linear velocity to medium- I 4 as it passes from spool: Hi to spool: I2. If this frictional engagement is'inadec uateg. medium I4 will slip relativetorcapstanr Iii-and" variations in the linear: velocity; of mediumf I4 will :result; The consequenttime variations :in the induced rvoltageiin-head- 'I81will 'causeunsatisfactory reproduction of the-signaland hence render-recording and. reproduction unsatisfactory.

I have discovered that particularly good frictionalf engagement: can be r achieved: between medium I4 and capstan: I.6 -.=ifttheisurfacezof it the 0 rough spots.

latter is made of a lead alloy, such as a lead-tin alloy. A construction of wheel IS in accordance with this aspect of my invention is shown in Figure 4 which is a cross section view through the axis IVIV, Figure l, and which shows a capstan having an inner supporting portion 48 having a lead alloy covering 50. I have found that a particularly suitable material for the outer sheath of capstan I5 is a lead-tin alloy comprising 65% lead and 35% tin. Other materials containing lead give satisfactory performance, however.

A further feature of my invention resides in the use:of-Tpressure pad 52, Figure l, which is yieldably supported by cantilever spring 54 from mounting-plate 34 as will be evident from examination ofiFigure 2. Pressure pad 52 is of felt or similar material capable of exerting uniform-pressure against capstan I6. When mounting plate 34 is rotated-Zin the counterclockwise direction,: springw 54;:isaccordinglyrotated a direction-rcausing-pressurepad 5 2 1 topress against the surface of capstan I6: Thus, the: pressure exerted: by; pressurepfad .52 against" capstan; I6 is-determined bythe-position of switch .46'fl1'ld? hence by: the direction of travel zof' medium I41:

It will be observed thatawhenrtheunit is-Fopw cratingin' the 'reversedirection with medium I4 being-rewound on spool IQ from spool I2, capstan: Iii-nevertheless rotates in theclockw-isedirection; against the-'motion of the medium I 4-: In-iaddition, as pressure pad 52 bears-against-mediumr I i and presses this medium against capstanII-i; atrestrainingqforce is. imparted tomedium I41 which causes the medium I4 to be under-essen'-= tially; uniform-and constant tension depending upon: the pressure exerted by pressure pad 52 thereby-insuring that said medium-iwill be-rre-P wound-smoothly and-firmly onto'spool- IQ. As' pressure. pad 52. bears against mediuml i -in'this condition, medium I4 tends to clean-capstanfifi: thereby rendering the surface of sheath- 5B smooth and symmetrical. This -maintains the capstan. I6 in good aoperating conditionv so thatv when it is operated in the forward position the: linear. velocity imparted to medium I4 is constant.

In-the case of a magneticrecorder and: repro. ducer it is. particularly important that the cap stanv I6.be. of uniform radiusand have no. fiat or Otherwise periodic variations" in linear. velocity are imparted to medium I 4- andwow results. It will be observed-that with the system described herein, the capstan I6 is-pol. ished in direct proportion to the amount of use. of the unit so that the polishing action .correspends-to the natural effecttending to cause capstan I 5. to deviate froma perfectly symmetrical condition.

Mechanisms having features in common with the presentinvention' are-disclosed and claimed in-1ny5copending application? (Case:46,502) and: the copending application of myself and Hugh'A'. Howell.(Case 46 941.);

While I have shown a'particular' embodiment of my invention, it will; of course, be understood that I do not Wish to be limited" theretosince'; many modifications in: the'i-elementsi employed and the structure disclosed may be made without departing from the spirit and; ScQp'eJthereof; I;

of courseg contemplate .bythe appended claims;

to cover any such modifications as fall within the' true spirit and-scope of my invention.

I claim'as' my invention: 1. Acdrive mechanism .for imparting velocity tozaemedium:includinefaxcflfistrn:tmengBeeJSaIdi medium, mechanism to rotate said capstan so as i to the rotation thereof so as to cause said me dium to polish said capstan to a uniform radius.

2. A drive mechanism for imparting velocity.

to a medium including a capstan to engage said medium, mechanism to rotate said capstan so as normally to impart velocity to said medium, a drive selectively operable to move said medium in opposition to the rotation of said capStan a wheel and a pressure pad alternately engageable to urge said medium against said capstan, and elements connecting said wheel and said pressure pad to said drive so that said wheel engages when said medium moves with said capstan and said pressure pad engages when said medium moves in opposition thereto.

3. In combination a pair of medium supporting devices, a longitudinal flexible medium wound about said devices to be transferred therebetween, a capstan to engage said medium to tend to transfer said medium from one of said devices to the other, a unidirectional drive for said capstan, mechanism to urge said medium against said capstan including a pinch wheel and a pressure pad alternately engageable with said medium, a drive to tend to rotate said devices in opposed directions to tend to wind said medium thereon,

said drive being adjustable to wind said medium in opposition to the rotation of said capstan,

said drive and said mechanism being interconnected so that said pressure pad engages said medium when said medium travels in opposition to the rotation of said capstan.

ELMER B. OFFUTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 64,078 Cotton Apr. 23, 1867 71,991 Cotton Dec. 10, 1867 1,856,272 Summers May 3, 1932 2,069,595 Thomas Feb. 2, 1937 2,341,636 Luehrs Feb. 15, 1944 2,408,320 Kuhlik Sept. 24, 1946 2,426,838 Miller Sept. 2, 1947 FOREIGN PATENTS Number Country Date 459,035 Great Britain Dec. 31, I936 

